Nerium oleander, a member of the Nerium species, is an ornamental plant widely distributed in subtropical Asia, the southwestern United States, and the Mediterranean. Its medical and toxicological properties have long been recognized. It has been proposed for use, for example, in the treatment of hemorrhoids, ulcers, leprosy, snake bites, cancers, tumors, neurological disorders, cell-proliferative diseases.
Extraction of components from plants of Nerium species has traditionally been carried out using boiling water, cold water, or organic solvent.
ANVIRZEL™ (U.S. Pat. No. 5,135,745 to Ozel), which is commercially available, contains the concentrated form or powdered form of the hot-water extract of Nerium oleander. Muller et al. (Pharmazie. (1991) September 46(9), 657-663) disclose the results regarding the analysis of a water extract of Nerium oleander. They report that the polysaccharide present is primarily galacturonic acid. Other saccharides include rhamnose, arabinose and galactose. Polysaccharide content and individual sugar composition of polysaccharides within the hot water extract of Nerium oleander have also been reported by Newman et al. (J. Herbal Pharmacotherapy, (2001) vol 1, pp. 1-16). U.S. Pat. No. 5,869,060 to Selvaraj et al. pertains to extracts of Nerium species and methods of production. To prepare the extract, plant material is placed in water and boiled. The crude extract is then separated from the plant matter and sterilized by filtration. The resultant extract can then be lyophilized to produce a powder. U.S. Pat. No. 6,565,897 (U.S. Pregrant Publication No. 20020114852 and PCT International Publication No. WO 2000/016793 to Selvaraj et al.) discloses a hot-water extraction process for the preparation of a substantially sterile extract.
Erdemoglu et al. (J. Ethnopharmacol. (2003) November 89(1), 123-129) discloses results for the comparison of aqueous and ethanolic extracts of plants, including Nerium oleander, based upon their anti-nociceptive and anti-inflammatory activities.
Organic solvent extracts of Nerium oleander are also disclosed by Adome et al. (Afr. Health Sci. (2003) August 3(2), 77-86; ethanolic extract), el-Shazly et al. (J. Egypt Soc. Parasitol. (1996), August 26(2), 461-473; ethanolic extract), Begum et al. (Phytochemistry (1999) February 50(3), 435-438; methanolic extract), Zia et al. (J. Ethnolpharmacol. (1995) November 49(1), 33-39; methanolic extract), and Vlasenko et al. (Farmatsiia. (1972) September-October 21(5), 46-47; alcoholic extract).
A supercritical fluid extract of Nerium species is known (U.S. Pat. Nos. 8,394,434, 8,187,644, 7,402,325) and has demonstrated efficacy in treating neurological disorders (U.S. Pat. Nos. 8,481,086, 9,220,778, 9,358,293, US 20160243143A1) and cell-proliferative disorders (U.S. Pat. No. 8,367,363).
Triterpenes are known to possess a wide variety of therapeutic activities. Some of the known triterpenes include oleanolic acid, ursolic acid, betulinic acid, bardoxolone, maslinic acid, and others. The therapeutic activity of the triterpenes has primarily been evaluated individually rather than as combinations of triterpenes.
Oleanolic acid is in a class of triterpenoids typified by compounds such as bardoxolone which have been shown to be potent activators of the innate cellular phase 2 detoxifying pathway, in which activation of the transcription factor Nrf2 leads to transcriptional increases in programs of downstream antioxidant genes containing the antioxidant transcriptional response element (ARE). Bardoxolone itself has been extensively investigated in clinical trials in inflammatory conditions; however, a Phase 3 clinical trial in chronic kidney disease was terminated due to adverse events that may have been related to known cellular toxicities of certain triterpenoids including bardoxolone at elevated concentrations.
Compositions containing triterpenes in combination with other therapeutic components are found as plant extracts. Fumiko et al. (Biol. Pharm. Bull (2002), 25(11), 1485-1487) discloses the evaluation of a methanolic extract of Rosmarimus officinalis L. for treating trypanosomiasis. Addington et al. (U.S. Pat. Nos. 8,481,086, 9,220,778, 9,358,293, US 20160243143 A1) disclose a supercritical fluid extract (SCF; PBI-05204) of Nerium oleander containing oleandrin and triterpenes for the treatment of neurological conditions. Addington et al. (U.S. Pat. No. 9,011,937, US 20150283191 A1) disclose a triterpene-containing fraction (PBI-04711) of the SCF extract of Nerium oleander containing oleandrin and triterpenes for the treatment of neurological conditions. Jäger et al. (Molecules (2009), 14, 2016-2031) disclose various plant extracts containing mixtures of oleanolic acid, ursolic acid, betulinic acid and other components. Mishra et al. (PLoS One 2016 25; 11(7):e0159430. Epub 2016 Jul. 25) disclose an extract of Betula utilis bark containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components. Wang et al. (Molecules (2016), 21, 139) disclose an extract of Alstonia scholaris containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components. L. e Silva et al. (Molecules (2012), 17, 12197) disclose an extract of Eriope blanchetti containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components. Rui et al. (Int. J. Mol. Sci. (2012), 13, 7648-7662) disclose an extract of Eucaplyptus globulus containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components. Ayatollahi et al. (Iran. J. Pharm. Res. (2011), 10(2), 287-294) disclose an extract of Euphorbia microsciadia containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components. Wu et al. (Molecules (2011), 16, 1-15) disclose an extract of Ligustrum species containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components. Lee et al. (Biol. Pharm. Bull (2010), 33(2), 330) disclose an extract of Forsythia viridissima containing a mixture of oleanolic acid, ursolic acid, betulinic acid and other components.
Oleanolic acid (O or OA), ursolic acid (U or UA) and betulinic acid (B or BA) are the three major triterpene components found in PBI-05204 (PBI-23; a supercritical fluid extract of Nerium oleander) and PBI-04711 (a triterpene-containing fraction 0-4 of PBI-05204). We (two of the instant inventors) previously reported (Van Kanegan et al., in Nature Scientific Reports (May 2016), 6:25626. doi: 10.1038/srep25626) on the contribution of the triterpenes toward efficacy by comparing their neuroprotective activity in a brain slice oxygen glucose deprivation (OGD) model assay at similar concentrations. We found that PBI-05204 (PBI) and PBI-04711 (Fraction 0-4) provide neuroprotective activity.
Extracts of Nerium species are known to contain many different classes of compounds: cardiac glycosides, glycones, steroids, triterpenes, polysaccharides and others. Specific compounds include oleandrin; neritaloside; odoroside; oleanolic acid; ursolic acid; betulinic acid; oleandrigenin; oleaside A; betulin (urs-12-ene-3β,28-diol); 28-norurs-12-en-3β-ol; urs-12-en-3β-ol; 3β,3β-hydroxy-12-oleanen-28-oic acid; 3β,20α-dihydroxyurs-21-en-38-oic acid; 3β,27-dihydroxy-12-ursen-38-oic acid; 3β,13β-dihydroxyurs-11-en-28-oic acid; 3β,12α-dihydroxyoleanan-28,13β-olide; 3β,27-dihydroxy-12-oleanan-28-oic acid; and other components.
Viral hemorrhagic fever (VHF) can be caused by five distinct virus families: Arenaviridae, Bunyaviridae, Filoviridae, Flaviviridae, and Paramyxoviridae. The Filoviruses, e.g. Ebolavirus (EBOV) and Marburgvirus (MARV), are among the most pathogenic viruses known to man and the causative agents of viral hemorrhagic fever outbreaks with fatality rates of up to 90%. Each virion contains one molecule of single-stranded, negative-sense RNA. Beyond supportive care or symptomatic treatment, there are no commercial therapeutically effective drugs and no prophylactic drugs available to treat EBOV (Eboval virus) and MARV (Marburg virus) infections, i.e. filovirus infections. Five species of Ebolavirus have been identified: Taï Forest (formerly Ivory Coast), Sudan, Zaire, Reston and Bundibugyo.
The Flaviviruses are positive, single-stranded, enveloped RNA viruses. They are found in arthropods, primarily ticks and mosquitoes, and cause widespread morbidity and mortality throughout the world. Some of the mosquito-transmitted viruses include Yellow Fever, Dengue Fever, Japanese Enchephalitis, West Nile Viruses, and Zikavirus. Some of the tick-transmitted viral infections include Tick-borne Encephalitis, Kyasanur Forest Disease, Alkhurma Disease, Omsk Hemorrhagic Fever. Although not a hemorrhagic infection, Powassan virus is a Flavivirus. 
Oleandrin, and an extract of Nerium oleander have been shown to prevent the incorporation of the gp120 envelope glycoprotein of HIV-1 into mature virus particles and inhibit viral infectivity in vitro (Singh et al., “Nerium oleander derived cardiac glycoside oleandrin is a novel inhibitor of HIV infectivity” in Fitoterapia (2013) 84, 32-39).
Oleandrin has demonstrated anti-HIV activity but has not been evaluated against many viruses. The triterpenes oleanolic acid, betulinic acid and ursolic acid have been reported to exhibit differing levels of antiviral activity but have not been evaluated against many viruses. Betulinic acid has demonstrated some anti-viral activity against HSV-1 strain 1C, influenza A H7N1, ECHO 6, and HIV-1. Oleanolic acid has demonstrated some anti-viral activity against HIV-1, HEP C, and HCV H strain NSSB. Ursolic acid has demonstrated some anti-viral activity against HIV-1, HEP C, HCV H strain NSSB, HSV-1, HSV-2, ADV-3, ADV-8, ADV-11, HEP B, ENTV CVB1 and ENTV EV71. The antiviral activity of oleandrin, oleanolic acid, ursolic acid and betulinic acid is unpredictable as far as efficacy against specific viruses. Viruses exist against which oleandrin, oleanolic acid, ursolic acid and/or betulinic acid have little to no antiviral activity, meaning one cannot predic a priori whether oleandrin, oleanolic acid, ursolic acid and/or betulinic acid will exhibit antiviral activity against particular genuses of viruses.
Barrows et al. (“A screen of FDA-approved drugs for inhibitors of Zikavirus infection” in Cell Host Microbe (2016), 20, 259-270) report that digoxin demonstrates antiviral activity against Zikavirus but the doses are too high and likely toxic. Cheung et al. (“Antiviral activity of lanatoside C against dengue virus infection” in Antiviral Res. (2014) 111, 93-99) report that lanatoside C demonstrates antiviral activity against Dengue virus. Human T-lymphotropic virus type 1 (HTLV-1) is a retrovirus belonging to the family Retroviridae and the genus deltaretrovirus. It has a positive-sense RNA genome that is reverse transcribed into DNA and then integrated into the cellular DNA. Once integrated, HTLV-1 continues to exist only as a provirus which can spread from cell to cell through a viral synapse. Few, if any, free virions are produced, and there is usually no detectable virus in the blood plasma though the virus is present in genital secretions. HTLV-1 predominately infects CD4+ T-lymphocytes and causes adult T-cell leukemia/lymphoma (ATLL)—a rare, yet aggressive hematological malignancy with high rates of therapy-resistance and generally poor clinical outcomes, in addition to several autoimmune/inflammatory conditions, including infectious dermatitis, rheumatoid arthritis, uveitis, keratoconjunctivitis, sicca syndrome, Sjögren's syndrome, and HAM/TSP, among others. HAM/TSP is clinically characterized by chronic progressive spastic paraparesis, urinary incontinence, and mild sensory disturbance. While ATLL is etiologically linked to viral latency, oncogenic transformation, and the clonal expansion of HTLV-1-infected cells, the inflammatory diseases, such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), are caused by autoimmune and/or immunopathological responses to proviral replication and the expression of viral antigens. HAM/TSP is a progressive neuroinflammatory disease that results in the deterioration and demyelination of the lower spinal cord. HTLV-1-infected circulating T-cells invade the central nervous system (CNS) and cause an immunopathogenic response against virus and possibly components of the CNS. Neural damage and subsequent degeneration can cause severe disability in patients with HAM/TSP. The persistence of proviral replication and the proliferation of HTLV-1-infected cells in the CNS leads to a cytotoxic T-cell response targeted against viral antigens, and which may be responsible for the autoimmune destruction of nervous tissues.
Even though cardiac glycosides have been demonstrated to exhibit some antiviral activity against a few viruses, the specific compounds exhibit very different levels of antiviral activity against different viruses, meaning that some exhibit very poor antiviral activity and some exhibit better antiviral activity when evaluated against the same virus(es).
A need remains for improved pharmaceutical compositions containing oleandrin, oleanolic acid, ursolic acid, betulinic acid or any combination thereof that are therapeutically active against specific viral infections.